To attenuate the optical signal emitted by a solid-state light source such as a laser diode, various coatings, diffractive optical elements, light-absorbing materials and/or active opto-electronic elements are typically employed.
For example, one common way to provide attenuation of an optical signal is to apply a transmission control coating to a glass element such as a slide or lens. The glass element is then sealed (e.g., via a glass-frit process) onto a metallic header can (e.g., a transistor outline (TO) can) that is welded to a header on which a solid-state light source is mounted. The degree of attenuation provided by the glass element is dependent on its tilt with respect to the plane of the light source and on the type of transmission control coating composition used. A smaller tilt angle provides less attenuation, while a larger tilt angle provides more attenuation. The tilt angle also affects the amount of light that can be reflected back to a photodetector for monitoring the light emitted by the light source. Disadvantages associated with the use of such a glass element include the complexity of determining the required tilt angle for a given attenuation, the required transmission control coating composition when the tilt angle might be subject to variations, the number of parts, and the complexity of assembling the parts.